(510av) Ab Initio Study Of Self-Assembled Monolayers Of Oligo Phenylene Ethynylene On Gold Surfaces

We present the study of interactions of oligo phenylene ethynylene (OPE) self-assembled monolayer (SAM) on the Au (111) surface using ab initio density functional theory calculations. In an first stage [1], we performed a full optimization including all atoms in the OPE and in the slab to better understand OPE adsorption on the surface. It was found that OPE has two energetically favorable adsorption sites on the Au surface with relatively different molecular geometries. A non-top site adsorption greatly modifies the (111) surface structure; however, the extensive electron interactions enable a delocalized electron density distribution, implying an improved conductivity between OPE and Au; and the top site which is 0.9 eV higher in energy than the non-top and features weaker Au-S bonds. Interestingly the on top configuration shows a strong spin imbalance along the molecule and the non-top shows a small spin imbalance on the surface. This feature is of strong interest for the development of resonators for the detection of chemical and biological agents. We have also studied calculated the frequency spectrum of these SAMs, which yield deformations in the gold surface yielding peak frequency shifts specific to each absorption site. Recent advances on this line of work will be presented.

[1] L. Miao and J. M. Seminario, "Electronic and structural properties of oligo phenylene ethynylenes on Au(111) surfaces," J. Chem. Phys., vol. 18, pp. 184706 (1-7), , 2007.